Linking models for improved groundwater flood simulation

Oxford in flood, July 2007

River and groundwater model domains

Increased awareness of the significance of groundwater flooding, as well as new legislation, are drivers for improved understanding of the risk associated with this form of flooding. The BGS has been undertaking research on one of the main groundwater flood settings; where relatively large river systems are in good hydraulic connection with low storage permeable superficial deposits underlain by impermeable bedrock. With better understanding of this flood setting has come the opportunity to develop more sophisticated flood simulation models. The linking of existing models which address components of flooding provides a cost-effective means of developing integrated flood risk management tools. The Open Modelling Interface (OpenMI) is a system which enables the linking of models with different spatial and temporal representations.

The benefits and challenges of using OpenMI to link existing models of flood-prone areas are being explored within a project involving BGS, HR Wallingford and Innovyze. This uses a case study from the River Thames floodplain in the city of Oxford, where stand-alone OpenMI-compliant river and groundwater models were available. The model system being developed couples the existing Environment Agency river hydraulic model for the Oxford reach of the Thames (originally in ISIS but converted to InfoWorks RS for this project) with the BGS groundwater model of the floodplain gravels (ZOOMQ3D). The river model is 1D with linked storage zones on the floodplain. The finite difference groundwater model is single layered. The models are coupled at the river and on the floodplain using leakage nodes.

Different model structures and resolutions mean that groups of groundwater model nodes have had to be assigned to river model reaches and flood storage zones. Initial results, based on the July 2007 flood in Oxford, have shown that the model linkage can greatly improve the simulation of groundwater level response during such events. Work is ongoing to develop the linked model to allow better quantification of groundwater flood risk in the city.

Relevant publications

MacDonald, D M J, Dixon, A, Newell, A J and Hallaways, A.  2012.  Groundwater flooding within an urbanised flood plain.  Journal of Flood Risk Management, 5, 68–80.

MacDonald, D M J, Bloomfield, J P, Hughes, A G, Macdonald, A M, Adams, B, McKenzie, A A.  2008.  Improving the understanding of the risk from groundwater flooding in the UK.  Proceedings of FLOODrisk 2008, European Conference on Flood Risk Management, Oxford, UK, 30 September to 2 October 2008. CRC Press, The Netherlands.

Contact

Contact David Macdonald for more information